In this episode Shahriar explores the cause of failure of an Agilent E4405B ESA 13.5GHz spectrum analyzer. In a previous episode, an E4407B version of the ESA was repaired and upgraded which is helpful in debugging and analyzing this instrument. The instrument displays LO Unlock which is a familiar problem. After an overview of the system block diagram, the LO signal path is traced and analyzed for problems.
After some investigation, the problem appears to be identical to the E4407B model repaired before! The Hittite (Analog Devices) divide-by-4 static divider unit has failed and does not divide correctly at high frequencies. The component is replaced which restores the instrument’s functionality.
The LCD screen of the unit is also very dim. The CCFL tube and the inverter are replaced with an LED back light instead. The unit then produces a bright and vibrant graphs and text. The performance of the instrument is verified with a Keysight MXG signal generator.